This invention relates to a rotary unit, such as a bearing or a pulley unit, having a clutch function.
A full-automatic washing machine-has a motor-driven main rotary shaft, a first output shaft coupled to and driven by the main rotary shaft, and a pulsator mounted on and rotated by the first output shaft. It may further include a second tubular output shaft provided around the first output shaft and driven by the main rotary shaft to drive a washing tub mounted on the second shaft together with the pulsator.
Ordinarily, the second output shaft of such a full-automatic washing machine is rotatably supported by a bearing mounted on the housing. Thus, the second output shaft may be rotated together with the rotating first output shaft. Some full-automatic washing machines are provided with a one-way clutch and a band brake to prevent the second output shaft from rotating together with the first output shaft.
Such a one-way clutch has to be mounted in close proximity to the bearing supporting the second output shaft. Thus, if they are designed to be assembled separately, such assembly work tends to be troublesome and time-consuming.
Unexamined Japanese Patent Publication 54-109557 proposes a solution to this problem. It discloses a bearing with a built-in clutch comprising, as shown in FIGS. 13 and 14, an outer ring 50, an inner ring 51, balls 52 and sprags 53 disposed between the outer and inner rings 50 and 51, and means for moving the sprags 53 into and out of engagement with cylindrical surfaces 54 and 55 of the outer and inner rings 50 and 51.
Unexamined Japanese Patent Publication 61-228153 discloses a belt transmission for transmitting the rotation of a crankshaft of an automobile to a rotary shaft of an engine auxiliary such as an alternator, which is large in inertia and thus tends to rotate at a substantially constant speed.
This belt transmission includes a one-way clutch mounted between the rotary shaft of the engine auxiliary and a pulley supported on the rotary shaft. It transmits the rotation of the crankshaft to the rotary shaft while the angular velocity of the crankshaft, which is changing minutely during one rotation, is increasing, and cuts off transmission while the angular velocity is decreasing.
Namely, while the angular velocity of the crankshaft is increasing, the one-way clutch engages, coupling the rotary shaft of the engine auxiliary to the pulley, so that the rotation of the crankshaft is transmitted to the rotary shaft. When the rotary shaft begins to rotate faster than the pulley, the one-way clutch will disengage, letting the rotary shaft rotate freely.
This belt transmission can prolong the life of the belt and reduce the belt slipping sounds by preventing slipping between the pulley and the belt.
But if such a one-way clutch is mounted directly between the rotary shaft and the pulley, radial and moment loads that act on the pulley will be applied directly to the clutch, making high-precision operation of the clutch impossible. Also, the life of the clutch will be shortened.
This problem is solved by supporting the pulley by a bearing. But it is troublesome and time-consuming to assemble and mount the one-way clutch and the bearing separately from each other.
The bearing/clutch assembly shown in FIGS. 13 and 14 can be modified into an easy-to-assemble pulley unit with a clutch function by replacing its bearing outer ring 50 with a pulley.
But the clutch/bearing assembly shown in FIGS. 13 and 14, or the pulley unit with a clutch function as modified in the abovesaid manner, has a problem in that its axial length is rather large because its balls 52 and sprags 53 are arranged axially in series.